U.S. Pat. No. 3,158,017 issued Nov. 24, 1964 entitled BURGLAR PROOF SAFE LOCKING BOLT ASSEMBLY is illustrative of a typical prior art safe door construction of the type with which the present invention is concerned. Basically, the types of safe doors shown in this patent comprise a massive body provided with a circular recess defining an annular wall. Bolt guiding bores extend radially through this wall for receiving locking bolts. The bolts in turn may be retracted and extended by an appropriate cam plate received in the recess and arranged to rotate between first and second positions. The inner ends of the bolts are provided with grooves receiving the outer edge of the cam plate and appropriate cam slots are provided through which pins extending transversely of the grooves in the ends of the bolts pass to hold the bolts captive to the cam plate. The arrangement is such that all the bolts involved, normally three spaced at 120.degree. are simultaneously retracted or extended by rotations of the cam plate through a given circumferential distance.
One of the common ways of burglarizing safes of the above type is to drill into the safe body wall from the side and punch back the locking bolts using a sledge hammer and a punch or metal rod. If the three bolts involved can be forced radially into the door structure, then the door can readily be removed and provide access to the safe.
The above-mentioned prior patent illustrates one manner of frustrating such attempts to burglarize a safe. More particularly, in accord with the teachings of this patent there is provided a triangular shaped plate member cooperating with the normally provided cam plate to distribute any inward force exerted on a bolt to the other two bolts involved thereby tending to drive these latter bolts outwardly.
Another means of dealing with the above problem is disclosed in part in my copending U.S. Pat. application Ser. No. 68,948 filed Aug. 23, 1979 and entitled SAFE DOOR. In this latter invention, the cam plate itself is appropriately dimensioned and coupled to the inner ends of the bolts in such a manner that it serves to absorb much of a radially inwardly directed blow against one of the bolts, the action in effect causing the cam plate to engage the opposite wall of the recess so that the whole strength of the door body absorbs such shock.